Many high valued objects are buried near the surface of the earth in soil. These include utility lines and equipment, unexploded ordnance, tunnels, coffins and graves, hazardous waste and more. Seismic detection of small buried objects shallower then 20 ft has been occasionally successful but has not been reduced to a standard practice. It has proven difficult because of the high frequencies of seismic waves required—up to 2500 Hz.
Seismic detection is also made more difficult because of heterogeneity often encountered near the surface of the soil. The heterogeneous soil conditions cause variations in coupling of seismic sources and receivers with the soil. The heterogeneous soil conditions also impact seismic wave velocities and contribute to noise in seismic measurements. These factors typically result in significant losses in seismic signals.
Exploration Seismic Reflection profiling and the standard Common Depth Point seismic acquisition can have subsurface point redundancy or “fold” of 60 or more, i.e. there are 60 channels of data used to sum the energy at one point in the image. This redundancy improves signal to noise ratios, overcoming seismic noise. Near surface targets must be detected in relatively higher levels of seismic reverberation. For seismic detection of shallow objects in the top 20 feet, much higher values of redundancy are necessary to achieve the array gain and bring signal above the scattered reverberation off the heterogeneities.
Improved systems and methods for detecting shallow buried objects is desired.